There are several well known types of electrical raceway systems which are designed to be placed in a floor. There are for example "underfloor raceways" as defined in Article 354 of the National Electrical Code and "cellular metal floor raceways" as defined in Article 356 of the National Electrical Code. Junction boxes designed for use in either of these two mentioned raceway systems, and conceivably in some other systems, can generally be referred to as junction boxes for use with a raceway system designed for placement in a floor.
As used herein the simple term "duct" or "raceway", or the phrase "raceway system for placement in a floor", or the like are intended to refer in a generic sense to an "underfloor raceway" or to a "cellular metal floor raceway" or both. Where the term "underfloor duct" or "underfloor raceway" is used it is intended as a reference to the particular type of system defined in Article 354 of the National Electrical Code.
The junction box disclosed in this application is designed primarily for use with an underfloor duct for use as part of an underfloor raceway, and is referred to as such in the description contained herein. It can, however, be used as part of a cellular metal floor raceway system and thus is generally referred to as a junction box for an electrical raceway system to be placed in a floor.
Underfloor duct is an electrical raceway system designed to be imbedded in the concrete floor of offices, classrooms, laboratories, manufacturing areas, supermarkets, etc., for the purpose of providing an enclosed raceway for wires and cables from their originating panel to their point of use.
Such an underfloor raceway system includes two types of ducts, namely feeder ducts and distribution ducts. Complementing these two types of ducts are junction boxes, support couplers and supports, horizontal and vertical elbows, power and telephone outlets and numerous cast and sheet metal fittings such as conduit adapters, change of direction duct runs, "Y" take-offs, etc.
A typical example of such an underfloor duct system, and particularly of a junction box for use therewith, is shown in U.S. Pat. No. 3,405,834 to Butler, et al., and assigned to the assignee of the present invention.
There are a number of disadvantages with a junction box structure like that of Butler, et al.
For example, the tunnel dividers which have previously been utilized with these junction boxes are factory installed, and cannot be removed without disassembly of the junction box. In order to provide a plurality of arrangements of ducts, the Butler, et al. design requires a separate model of junction box for each different duct arrangement, and thus a great many different junction boxes must be stocked by suppliers.
The duct separators utilized in junction boxes like that of Butler, et al., are also provided from the factory and give the customer little or no flexibility in changing the duct arrangement. Junction boxes that have been designed with removable separators require a special tool for this purpose and are labor intensive for the user.
Grounding of the ducts to a junction box like that of Butler et al. is accomplished with separate ground screws which must be screwed into engagement with the duct after the duct is inserted into the junction box.
Additionally, the junction box like that of the Butler, et al. patent provides no accommodation for different concrete floor depths. In order to provide for the different concrete floor depths that may be called for by an architect, these junction boxes have been supplied in various heights, so that for each different duct arrangement there must be a plurality of special junction boxes to provide for the different concrete floor thicknesses that can be utilized with that duct arrangement.
Although one manufacturer, the Walker division of Butler Manufacturing Company of Parkersburg, W. Va., has provided a junction box that can be modified to adjust its height, field conversion to another ring height of that device is very tedious. First the box cover must be removed. Then the trim ring assembly must be slowly adjusted upward until it is completely free of the adjusting screws. An extension collar is then added to the top side of the pan. New longer screws replace the short ones supporting the trim ring. The trim ring must then be remounted by starting the new longer screws and moving from screw to screw while lowering the trim ring back into the new extension collar. The cover is then replaced. This method is very labor intensive.
Thus it is seen that there is a need for a junction box design which provides a relatively small number of basic junction boxes which can be readily modified in the field to accommodate different duct arrangements and different concrete floor heights. Such a system would be greatly advantageous both economically and technically as compared to presently available systems.